Needs for antibacterial agents are on its way to growing widely, together with the diversification of life environment and a change in awareness of life. At present, antibacterial and antifungal chemical techniques are applied not only to a field related to people's lives but also to every industrial field such as the plastic industry, the electronic component industry and the like.
An antibacterial technique of the present invention is a series of techniques of persistently preventing the generation and growth of microorganisms (bacteria and fungi in particular) so as to previously prevent or avoid damage caused thereby.
For provisional sterilization, there are various physical techniques such as a method using ultraviolet rays or radiation, a heating method, a cooling method, a pressurizing method and the like. On the contrary to the provisional sterilization, an antibacterial technique is one that keeps a level of not more than sterilization and not less than bacteriostasis for a long period of time thereby suppressing the multiplication of microorganisms persistently. Incidentally, “sterilization” means a level at which microorganisms become extinct, while “bacteriostasis” means a level at which the multiplication of the microorganisms is suppressed.
Bacteria on which an antibacterial agent exhibits antibacterial activity are exemplified by gram-positive bacteria and gram-negative bacteria. Gram-positive bacteria are exemplified by pathogens such as Staphylococcus aureus, Streptococcus pyogenes and Clostridium botulinum. On the other hand, gram-negative bacteria are exemplified by pathogens such as Salmonella, Escherichia coli, Klebsiella pneumoniae, Haemophilus, Pseudomonas aeruginosa and Proteus. Meanwhile, fungi include ones parasitic on humans to bring about diseases, such as Trichophytons.
Thus, antibacterial agents are widely applied in order to persistently suppress the multiplication of microorganisms.
Additionally, antibacterial agents are also required to have both antifungal properties and antiviral properties, for example, virus disinfection and the like.
In human life spaces, there exist a variety of fungi and viruses.
Principal kinds of fungi are exemplified by blue mold, green mold, Mucor and Rhizopus. Though one popularly known as black mold can also be cited, it is difficult to specify the kind of fungi. In addition, in Europe, Neurospora crassa is also popularly known and stains on walls are often Cladosporium. 
On the other hand, principal kinds of viruses can be exemplified by Norovirus, Rotavirus, Rhinovirus, Coronavirus and respiratory syncytial virus. Viruses are classified into those having envelope and those not having envelope. Viruses having envelope are highly sensitive to a bactericidal agent effective against bacteria, while viruses not having envelope are highly resistant to the same. Of major viruses not having envelope, an RNA virus is exemplified by enterovirus such as poliovirus and Reoviridae, while a DNA virus is exemplified by adenovirus, papovavirus, the hepatitis B virus and the like. Enterovirus such as poliovirus, Coxsackievirus, echovirus and the like, i.e., RNA viruses not having envelope generally have strong resistance to various bactericidal agents, followed by adenovirus; on the contrary, viruses having envelope such as herpesvirus, Vaccinia virus and influenza virus are highly sensitive to the same. Among liquid chemicals, sodium hypochlorite is said to be the most effective bactericidal agent against any virus, even in a relatively low concentration.
Additionally, antibacterial agents are wide-ranging in kind so as to be variously used according to purposes. Antibacterial agents can roughly be classified into organic compound-based ones, inorganic compound-based ones and natural product-based ones.
Organic compound-based antibacterial agents are known to include: heterocyclic compounds such as thiazoles, imidazoles, pyridines, triazine and the like: organic nitrogen compounds such as amine, quaternary ammonium compounds, nitrile compounds and the like; organic oxygen compounds such as phenol, cresol, halogenated phenols and the like; organic sulfur compounds such as thiol and the like; and organic phosphorous compounds such as thiophosphoric acid and the like. The organic compound-based antibacterial agents are characterized by having an excellent antibacterial property against fungi. However, in the case where these are added to a film or a resinous molded article, there may arise volatilization or elusion, in which the effect becomes difficult to be kept. Moreover, since not a few of the organic compound-based antibacterial agents have toxicity, the use of them is sometimes restricted particularly in the fields of food, food processing and packaging from the viewpoint of consumer protection.
On the other hand, natural product-based antibacterial agents represented by chili extract, chitin, chitosan, wasabi extract, mustard extract, tea extract and hinokitiol are know. The natural product-based antibacterial agents are sometimes preferably used in view of safety, though there are problems of elusion and volatilization as in organic compound-based ones.
Moreover, inorganic compound-based antibacterial agents represented by silver are known, and these attain high levels of performance in the uses for resinous molded articles, films, fibers and the like. Inorganic compound-based antibacterial agents have difficulty in causing elusion or volatilization and tend to maintain the antibacterial effect for a long period of time and excellent in safety, which serves as the advantage of the inorganic compound-based antibacterial agents. However, in the case of attempting to disperse particles of Ag or Ag-loaded zeolite or the like in a resin, it is difficult to disperse the particles evenly and an antibacterial agent disposed inside is hard to act on outside fungi; therefore, the concentration of the added antibacterial agent is required to be increased in order to obtain a desired antibacterial effect. Hence it is indicated that the antibacterial effect (the antifungal effect in particular) is inferior to that in the organic compound-based ones. Furthermore, the use of expensive silver limits the applicable fields, which is indicated as a problem.
Against the above-mentioned background, attempts to fix a compound group having antibacterial property in a resin have been made and disclosed by two or more prior art references.
For example, in Patent Publication 1, a polymer-bonded antibacterial agent is disclosed as a polymer bonded to 2,2,6,6-tetramethyl-4-piperidine thereby suppressing elusion and volatilization.
Additionally, Patent Publication 2 discloses an antibacterial resin film which comprises a polyamide-based resin having a phosphonium sulfonate group, in which it is said that the antibacterial resin film has both antibacterial property and practical durability.
The polymer-bonded antibacterial agent disclosed by Patent Publication 1 and the antibacterial resin film disclosed by Patent Publication 2 both succeeded in bonding a compound group that has antibacterial property to a resin to fix it.
Patent Publication 3 discloses an antimicrobial resin characterized in that a polymer having carboxyl groups is provided such that a part of the carboxyl groups link to silver while the carboxyl groups bond to polyvalent metallic ion to form cross-linking bonds, in which it is said that the antibacterial property attained by virtue of silver ion is exhibited for a long period of time.
Furthermore, an antistatic agent having a bismethide acid group is disclosed in Patent Publication 4.